The present invention relates to a method of operating a materials handling machine.
Known materials handling machines such as back hoe loaders or mini excavators can perform material handling operations whilst stationary. Thus, the back hoe of a back hoe loader can be used to move material whilst the back hoe loader is stationary. Similarly, the working arm of a mini excavator can be used to move material while the excavator is stationary.
Such machines include stabilisers or the like which can be moved into engagement with the ground to help stabilise the machine whilst performing material handling operations. In one example the back hoe loader has a stabiliser on each side of the back of the machine. Each stabiliser can be individually lowered into contact with the ground. It is often advantageous to lower the stabilisers into engagement with the ground such that the rear wheels of the back hoe loader are lifted from the ground. This provides for a more stable arrangement since the elastomeric tyres of the back hoe loader then do not carry any of the weight of the back hoe loader.
Similarly, known excavators have a blade at the front of the machine running transversely. This blade can be lowered into engagement with the ground to help stabilise the machine.
The stabilisers are lowered into engagement with the ground by operating hydraulic rams or the like.
When setting up to dig a trench or the like when the vehicle is stationary, one of the first operations performed by the operator is to move the stabilisers into engagement with the ground. In order to save time, the operator will typically fully actuate the control lever or levers that deploy the stabiliser or stabilisers. This can put a high demand on the hydraulic pump which supplies hydraulic oil to the rams or the like which move the stabilisers. This in turn puts a high demand on the engine that drives hydraulic pump. Because deployment of the stabilisers is one of the first operations performed, the operator may be running the engine at an idle speed. Certain scenarios may cause the engine to lug down (i.e. slow down significantly below a normal idle speed) or even stall. Thus, consider the scenario where the machine has been left unused overnight in a cold climate. The operator, starting work for the day will enter the cab, start the engine, and almost immediately then deploy the stabilisers. Because the engine has not properly had time to warm up, and because the hydraulic oil is cold, the full deployment of the stabilisers causes a high load to be applied to the engine, which as mentioned above, may be running at an idle speed. This high load may be sufficient for the engine to “lug” down, i.e. slow down significantly below a normal idle speed, or may even cause the engine to stall. Clearly this is inconvenient for the operator since it causes delays.